<p>Toggles the screen-based linetype mode of the current drawing. 
<br />If this mode is activated, linetypes are optimized for a computer
screen. All lines are displayed with a screen based line width
(lines don't get wider when zooming in) and all patterns are shown as fixed,
pixel based patterns on screen (dashes don't get longer when zooming in). 
<br />If this mode is off, line widths and linetypes are shown in
drawing units (default).</p>
